arXiv subjects

Thomas Morand

Publications and source records attributed to Thomas Morand.

3 recordsLinked to original sources

arXiv2026

Multi-type Galton-Watson processes in dynamical environments

We define a model of multi-type Galton-Watson processes in dynamical environments where the environment evolves according to a dynamical system (X,T). Three behaviours are possible: uniformly subcritical, critical, and uniformly supercritical. We provide a criterion to determine the regime of a multi-type Galton-Watson process in dynamical environments. We study the continuity of the probability of extinction q in the uniformly supercritical case.

math.DS↗

arXiv2025

Numerical bounds on the regularity of an invariant function: Probability of extinction of Galton-Watson processes in dynamical environments

We study the Lyapunov exponents of models that are close to skew product systems over a C__ uniformly expanding transformation of the circle. For a continuous fibre map $\phi$, analytic, increasing, and convex in the fibre variable, we consider the smallest invariant function q satisfying q(x) = $\phi$(x, q(T x)). We provide rigorous numerical bounds on two Lyapunov exponents (the fibre exponent and the base exponent), and present algorithms to compute these bounds effectively. We then apply this framework to Galton-Watson processes in dynamical environments in the uniformly supercritical case. The probability of extinction q of the process is the invariant function of the associated system. Using the previously computed Lyapunov exponents, we control the H{\"o}lder regularity and differentiability class of the probability of extinction.

math.DS↗

arXiv2024

Galton-Watson processes in dynamical environments

We define a model of Galton Watson processes in dynamical environments where the environment evolves according to a dynamical system (X, T). Three behaviours are possible: uniformly subcritical, critical, and uniformly supercritical. We study the extinction probability q in the uniformly supercritical case. In particular, we investigate the regularity of this application as a function of the environment x. In the critical case, we study the set of bad environments N (where the probability of extinction is one), which is T -invariant. We give its Hausdorff dimension in some cases.

math.DS↗